Portable equatorial sundial



Dec. 13, 1960 S. K. HALL PORTABLE EQUATORIAL SUNDIAL.

Filed April 30, 1958 su/v 56 Fig.2

(v coRREcTmN TABLE FOR SAN maso Stephen K. Hall 4445 lNr/ENTOR.

The present invention relates to a small universal sundial which is not only portable for ease of handling and transportation but is completely self-contained and such in construction that it may be reliably used to ascertain standard or zone time with a reasonably high degree of accuracy anywhere in the world.

rfhe preferred embodiment of the concept illustrated in the accompanying drawing has been designed with the thought in mind of sale to prospective users in gift and toy shops and stores and by book sellers and others offering educational devices of a novelty character to purchasers. ln carrying out the inventive idea a construction has been adopted which should be of value in schools to demonstrate the theory of time and the earths movement in the solar system.

The invention is one which requires no fixed mounting or determination of the meridian for that part of the device which is described as a base is provided with a directly visible camera-type universal level and a small but reliable magnetic compass, these components being permanently embedded or otherwise mounted on the base. Then, too, the device has been constructed with the thought in mind that it may be successfully used indoors by a window or wherever direct sunlight is available during spring, fall, summer or winter seasons.

Briefly summarized, the invention comprises a portable base, a camera-type spirit level embodied in said base at a place of vantage and for isolated constant reference and viewing, a magnetic compass carried by said base and positioned on the base for ready usage, a sundial provided with a gnomon and a suitably graduated equatorial circle with which a shadow from said gno-mon may cooperatively register, and support means for said sundial adjustably mounted on said base and having at least one shadow arc coordinated with said gnomon and the graduations embodied in the equatorial circle.

It is also proposed in the development and commercialization of this invention to provide appropriate graduated scales for latitude and variation, brief instructions to explain time and longitude for students. Farticular emphasis is placed on the fact that the invention is characterized by an adjustable dial as a means of providing automatic time correction. Novel means is employed to support the dial and also the cooperating gnomon or shadow pin. With the construction stated and properly utilized clear vision of the shadow is permitted throughout the seasons of the year. The support means is such that the shadow pin is supported without confusing the shadow. In fact, it is believed that as a result of experimentation that no other type of support or dial arrangement can be satisfactorily provided without casting an unwanted additional shadow.

Stated somewhat more explicitly the base is in the form of a wooden or equivalent panel which is preferably but not necessarily rectangular in plan and has the desired spaced parallel longitudinal marginal edges. Properly paired brackets are fixed to the median portions of the marginal edges and they project above the top of the base or panel. A unique frame is hingedly mounted between the brackets. Means for clamping the brackets against the cooperating edge portions of the frame is provided so that the frame may be set and clamped to assume a position at relative to the plane of the top of the panel, or alternatively, swung to assume varying angular positions relative to said top. The sundial is carried by the frame and the sundial is in turn equipped with the novel shadow pin, said sundial being preferably transparent and suitably graduated and marked to provide the desired equatorial circle, a circle having a centered meridian index.

Other objects, features and advantages will become more readily apparent from the following description and the accompanying drawing` In the drawing, wherein like numerals are employed to designate like parts throughout the views:

` Fig. 1 is a plan view of the preferred embodiment of the novel portable sundial.

Fig. 2 is a section on a slightly enlarged scale taken on the plane of the line 2--2 of Fig. l, looking in the direction of the arrows.

Fig. 3 is a section on the irregular line 3-3 of Fig. 2.

Fig. 4 is a fragmentary bottom lplan showing the correction table.

Fig. 5 is a fragmentary detail view showing one of the brackets and the latitude reckoning scale.

Referring now to the drawing and particularly to Fig. l the base 6 is preferably in the form of a rectangular panel. An experimental model has been made of wood, but of course, any suitable lightweight material will do. The spaced parallel longitudinal edges or margins are denoted at 8 and the transverse ends at 110 and 12. For convenience of description the end 12 is at the north and embedded in the top surface 14 adjacent to but inwardly ofthe end is a camera-type universal level i6. The aforementioned magnetic compass 18 is embedded in the top inwardly of the south or opposite end l0. Adjacent to the compass there is a suitably embedded pin 20 which is used as a reference mark to correct for magnetic variation. Also, there is a printed correction table or card containing a table mounted on the bottom and this table is here denoted by the numeral 22. ltwill be mentioned again later on.

The aforementioned transparent sundial, or clock d ial as it is sometimes referred to, is denoted by the numeral 24. It is made of a suitable transparent pane which is generally semicircular in plan. The upper straight across edge is denoted at 26. The circumferential edge is graduated to provide what is herein referred to as an equatorial circle 28. Themount or support means for the dial is broadly designated by the numeral 30 and is more specically referred to as a wooden or equivalent frame. This frame has a substantially semicircular cutout into which the graduated dial is fitted and centrally located as seen in Fig. 2. The peripheral marginal edge defining the perimeter limits of the cutout has a centralized channel or groove 32 formed therein as seen in Fig. 2 and into which the correspondingly shaped marginal edge of the dial is removably and adjustably seated and friction held. The peripheral surfaces 34 and 36 (Fig. 2) to the right and left of the dial are finished with a suitable light diffusing medium. In actual practice white enamel has been painted on these surfaces. The body portion 38 is hingedly mounted on a cross rod or trunnion ed, the end portions of which are screw-threaded and supported in simple brackets 42 (Fig. 3) suitably fastened to the marginal edges of the base. Appropriately knurled assembling and clamping nuts 44 are provided on the screwthreaded ends 46 and these serve in an obvious manner.

The horizontal base or panel is permanently fitted with the suitably arranged aforementioned level and magnetic V:mesmo compass. As the compass reading must be corrected for variation, the small brass or equivalent pin is set 15 east of the meridian or centerline. This provides for correction at the given locality, say San Diego, California. The folding 30, sometimes referred to as a -tiltable bracket, is hinged on the base in such a way that it can be elevated to an angle equal to 90 latitude. By way of the construction shown it can be locked in this position. Then too, with this arrangement, by passing the bolt or trunnion 40 through the narrow body portion of the frame this part is reinforced against breakage.

As before stated the frame is cut in the form of a semicircular arc. 'The shallow groove or keyway 32 allows the edge portion of the dial 24 to be inserted and removed and adjusted and as before stated the surfaces 34 and 36 on opposite sides are enameled white in order to clearly seeY the shadow. When the sundialis aligned with the meridian, the arc is parallel to the equator. For this reason the graduated perimeter portion 28 has been called the equatorial circle. Manifestly, the diameter of the curvate edge of the dial is such that it conforms with the groove or channel 32.` The angular freedom permits adjustment as before stated and the periphery of the dial is appropriately engraved with a clock scale wherein the divisions of smallest dimension indicate ten minutes in time. With reference now to the gnomon this is denoted by the numeral 48 and comprises a brass 'pin set perpendicularly through an opening provided therefor at the geometric center of the dial; The length of the pin is such that it subtends an angle ofV 231A degrees on either side of the dial at the periphery. The correction table 22. previously mentioned was calculated and printed for the area of San Diego.

The preferred mode of using the invention is as follows:

The user should see that the equatorial frame 30 is set at the correct angle in relation to the base.' This angle is 90 minus the latitude of the locality in which the time t check is to be made. In the drawing a small brass pin 50 (Fig. 5) is set in at least one end of the frame. When this pin is matched with a cooperating graduation on the scale 52 at the upper rounded end of bracket 42 the angle of elevation for the frame and its dial is correct, say for San Diego. Next the user refers to the card or table 22 on the underside of the base in order to read the time Vsetting opposite the calendar date. It is then necessary to rotate the transparent dial to a point where the meridian mark on the arc is opposite the above setting on the time scale. Then simply rotate the base until the compass needle points east or west on the medidianv line by an angle equal to the local variation. In the illustration this point 29 is set, as before mentioned at 15 east of the centerline. Manifestly, the base must be held horizontal by reference to the level 16. The shadow pin 48 will now be parallel to the earths axis, and the shadow cast on the white arcs or surfaces 34 and 36 will move at nearly the same angular rate of the earths rotation. Due to the correction introduced by offsetting the dial, the correct zone time may be read at the point where the shadow intersects the graduated time scale.

With further reference to Fig. 2 the shadow pin is linearly straight and the central portion 54 is appropriately mounted and supported at a predetermined spot, the geometric center of the dial. The projecting end portions to the left and right are differentiated by the numerals S6 and 58. It may be added that the dial is fitted into the keying groove so that it may be adjusted or shifted to correct for longitude and equation of time. The meridian mark is seen in Fig. l and denoted at 60.

In practice an angular scale of magnetic variation (not shown) may, perhaps should, be provided adjacent to the compass needle. Also, it should be kept in mind that it is within the purview of the concept to use a dial of translucent, as well as transparent, material for the clock dial, for if the shadow of the gnomon or pin were thrown on the back of a translucent dial, it could be easily read on the upper surface of such a dial.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be restorted to, falling within the scope of the invention as claimed.

What is claimed'as new is as follows:

1. For use Vin schools and elsewhere to implement and expeditiously demonstrate the theory of time and the movement of the earth in the solar system; a portable self-contained equatorial sundial comprising a base panel rectangular in plan and having spaced longitudinal marginal edges, a pair of opposed brackets fixed to median portions of said marginal edges and projecting slightly above the top of said panel, a frame having a lower horizontal edge portion in close proximity to, straight across, parallel with and hingedly mounted between said .brackets and extending transversely across the panel, manually regulatable means for clamping the brackets against cooperating vertical edge portions of the frame so that the frame may be set and clamped to assume a position of relative tothe plane of the top of the panel or, alternatively, swung to assume varying angular positions relative to said top, a one-piece transparency providing a sundial provided marginally with a suitably graduated time scale, a shadow pin joined intermediate its ends with said sundial and having its end portions projecting in opposite directions beyond and at right angles to opposite surfaces of the sundial, peripheral surfaces of portions of the frame coincident to and commensurate with the graduated time scale being light diffusing to cooperate with the shadows cast thereon by way'of said shadow-pin, the upper end portion of at least one bracket being rounded and provided with an easily viewable suitably arcuate and graduated latitude scale for functional cooperation with an indicating pin fixed on an adjacent marginal part of said frame to denote the angular elevation and position of use of the frame for a given locality, a level embedded in the top of the base panel at a north side of the frame, and a magnetic compass embedded in said top at the south side of the frame.

2. A portable school-room-type self-contained sundial primarily for use indoors comprising a portable base panel having spaced parallel longitudinal marginal edge portions, a directly visible magnetic compass mounted in said base adjacent one transverse end of the base and visible through the top of the panel, a directly visible spirit level also embodied in the top of said base but located adjacent the opposite transverse end of the panel, a pair of brackets fixed to median portions of said marginal edges and projecting a relatively short distance above the level of the top of the panel, at least one of said brackets having an arcuately rounded upper end provided on an easy-to-see side with graduations cooperating with said rounded end and defining a latitude scale, a block-like frame having a lower portion hingedly mounted between said brackets and extending transversely across the central portion of the top of the panel and disposed in approximate parallelism to the plane of said top, said frame being provided at one end with an outstanding indicating pin cooperable with the graduations on the aforementioned scale and serving to indicate the angle of tilt of the frame relative to the horizontal plane of the panel, said frame being relatively thick and having a semi-circular cutout dening an arcuate surface, said arcuate surface being provided midway between its front and rear sides with an open-ended groove providing a keyway, the half portions of the arcuate surface, to the left and right of the groove being coated with light diifusing paint, a sundial having an outer perimeter edge portion provided with a graduated clockdial and slidingly and removably keyed for retention and adjustment in said groove, said sundial being provided at a prerequisite point with a shadow pin having end portions projecting at right angles beyond cooperating at surfaces provided on the respective opposite sides of said sundial.

3. A novelty-type self-contained equatorial sundial which is compactly foldable and is easy to package, carry and erect for use comprising a portable base panel which is rectangular in plan and has spaced parallel longitudinal edges and transverse edges as Well as at top and bottom surfaces, a pair of lug-like clips secured respectively to opposed median portions of the longitudinal edges of said panel, said clips having limited portions rising above the top of the panel and providing brackets, the upper projecting end of at least one bracket being arcuately rounded and provided on an exterior side with suitably arranged graduations providing an angle-of-elevation scale, the upper end portions of said brackets being provided with bearing holes, a block-like frame having a semi-circular cutout, the peripheral surface of which is provided midway between the left and right main surfaces of the frame with a semi-circular keying groove which is commensurate with the peripheral surface and which has its ends open, a rod member extending through the lower portion of said frame, said lower portion being straight and disposed in parallelism above the top of the panel, said rod projecting beyond end portions of the frame and the projecting ends being screw-threaded and passing through the bearing holes in said brackets and the screw-threaded ends being provided with assembling and clamping nuts, the peripheral surface portions to the left and right of said groove being relatively wide in plan, easy to see and coated with shadow-exhibiting paint, a one piece transparent pane providing a sundial and generally semicircular in plan and having a circular marginal edge portion removably and adjustably keyed in said groove and provided with a clockdial and graduations, the straight across edge portion spanning the space between the mouth of the semi-circular cutout, and a shadow-pin operatively mounted in a median portion of the dial in a position to cooperate with the dial graduations and the aforementioned shadow-exhibiting surfaces, that end of the frame adjacent the rounded upper end of the aforementioned bracket being provided with an outstanding indicating pin cooperable with graduations on the aforementioned scale.

References Cited in the tile of this patent UNITED STATES PATENTS 2,192,750 Mead Mar. 5, 1940 2,415,433 Little Feb. 11, 1947 2,696,053 Royt Dec. 7, 1954 2,846,768 Putnam Aug. 12, 1958 FOREIGN PATENTS 607,597 Germany Jan. 3, 1935 700,983 Great Britain Dec. 16, 1953 

